westover



March 10, 1964 Filed NOV. 8, 1962 R. F. WESTOVER HYDRODYNAMIC PUMP OR EXTRUDER F/GJA PRESSURE 3 Sheets-Sheet 2 R. F. WESTOVER HYDRODYNAMIC PUMP OR EXTRUDER March 10, 19 64 3 Sheets-Sheet 3 Filed NOV. 8, 1962 OvO 33 3 93m $6 one owe United States Patent 3,123,861 HYDRQDYNAMEC PUMP 0R EXTRUDER Robert F. Westover, Princeton, NJ, assignor to Bell Telephone Lahoratories, incorporated, New York, N.Y., a corporation of New York Filed Nov. 8, 1962, Ser. No. 236,324- Claims. (Cl. 18-42) This invention relates to hydrodynamic pumps. More specifically it concerns a novel pump design useful for pumping viscous fluids, and is particularly well adapted for the extrusion of plastics.

Various pump designs have been proposed in the prior art for pumping highly viscous fluids. Certain of these are constructed according to a so-called fluid wedge principle. This form of pump is described in detail in United States Patents 2,777,394, 2,992,615 and 3,037,457. The present invention is directed to a modification of this pump construction which permits unexpected advantages over the prior art design. These and other aspects of the invention will become more evident from a consideration of the drawing in which:

FIG. 1 is a front section of a basic form of pump constructed according to the invention;

FIG. 2 is a perspective view partly cut away showing the detail of the pressure generating components of the P p;

FlG. 3A is a schematic representation of one form of pressure generating plate geometry also showing the pressure profile;

FIG. 3B is a schematic representation of an alternative form of pressure plate design;

FIG. 4 is a front section of a preferred form of device which is adapted for the extrusion of plastics;

FIG. 5 is a plan view of the slider pad plate of the extru-der of FIG. 4; and

FIG. 6 is a plot of output rate vs. pressure for the extruder of FIG. 4 using polyethylene.

FIG. 1 shows a hydrodynamic pump constructed using the principles of the invention. A sealed housing is made in two mating sections 11 and 12 which are assembled together by bolts 13 and 14. Within the housing is a chamber 15 which contains the rotor plate 16. The plate 16 is rotatably mounted on rotor shaft 17 in bearings 18 and 19. Bearing 18 is a radial bearing while bearing 19 is preferably a thrust bearing to accommodate back thrust on the rotor shaft. Aifixed to the interior portion of the housing section 12 is a slider pad plate 26 upon which a plurality of slider pads are disposed in radial juxtaposition. The construction and function of the slider pads will become apparent from the description of FIG. 2.

The inlet port 21 and outlet port 22 communicate with the interior chamber as shown. Machine bolts 23 and 24 secure the slider pad plate to the housing. O-ring seals 25, 26 and 27 maintain a fluid-tight relationship 'at vulnerable points in the assembly. For low viscosity fluids a liquid seal 23 around the rotor shaft is desirable. The recessed portions 29 and 36 in the slider pad plate are radially extending outlet grooves which can be seen in perspective in FIG. 2. The outlet grooves feed into ducts 3 1 and 32 which extend through the slider pad plate and terminate in a circumferentially extending chamber 33. The output fluid thereafter exits through port 22. A plurality of exit ports may be provided; however, it is often advantageous to have a single output location. An air bleed vent 34 is provided for removing residual fluid.

FIG. 2 illustrates the slider pad plate in greater detail. The slider pad plate is constructed of a plurality of sector-shaped surfaces such as 40, 41, 42 and 43. Each sector is bounded by feed slots 44, 45, 46 and 47. The

3,123,861 Patented Mar. 10, 1964 "ice feed slots communicate with the central feed port 21 as shown in FIG. 1. These grooves are preferably at least 50 mils deep for proper feeding of most materials. Spaced from the stationary slider pad plate is the rotor plate 16 which is mounted for rotation in one angular direction by the rotor shaft @17. The face of each slider pad is inclined in the direction of rotation of the rotor plate. Situated in each slider pad face are radially extending exit slots 48, 49 50 and 51. Associated with each exit slot is a passage such as 31 and 3 2 (FIG. 1) which terminates in the common circumferential output chamber 33 (FIG. 1).

The operation of the pump is relatively simple. The viscous fluid is introduced into the inlet port 21 and distributed into each feed slot. The motion of the rotor plate shears the fluid over the slider pads. The wedge action generates a pressure which increases toward the middle of the slider where the fluid is driven out the exit slot.

The pressure build-up is illustrated schematically in FIGS. 3A and 3B.- FIG. 3A shows an inclined surface 6t having a constant slope which represents the slider pad. The rotor surface is represented by'61. Relative motion between the two creates the indicated pressure profile within the fluid 62. The fluid is most adv-antageously introduced at the point of lowest pressure and the outlet at the point of maximum pressure although deviations from this may be used where desired.

FIG. 3B shows a slider pad of modified construction. Here the pressure increase is obtained by virtue of a step. The rotor plate surface 64- drives the fluid against the riser 65 of the slider pad and into the constricted region 66. The accompanying pressure profile is similar to that in FIG. 3A with the point of maximum pressure occurring at the step. For this reason the outlet slot is most advantageously formed adjacent the step.

Many alternative geometries for the slider pad plate are suitable. To obtain a positive pumping pressure it is only essential that one of the opposing plate surfaces have at least one region which is spaced more closely to the other plate surface than at least one other region. This also suggests the case of continuously varying spacmg.

It is apparent from this description that the slider pads can be located on the stationary plate or the rotary plate, or both. Alternatively, both plates are made rotatable. The construction of FIG. 1 permits a more direct approach to the feeding and expelling of the fluid than that encountered where inlet and outlet provision must be provided for in the rotary plate.

In another such modification a second slider pad plate is affixed to the interior of the chamber onto the housing section 11. In this case both the front and the rear surfaces of the rotor plate actively pump fluid. Such a construction doubles the pump capacity and equalizes the thrust between the rotor shaft and the housing.

The fluid feed is shown by way of example with an axially located inlet and fluid feeding into the feed grooves assisted by centrifugal force. While this arrangement is a desirable one, the feed may be located at the periphery of the slider pad plate or a dual feed arrangement may be used employing both central and peripheral feed. When pumping low viscosity fluids with a peripheral feed it is generally found necessary to maintain a positive pressure on the fluid at the inlet.

The outlet means is preferably a radial groove extending across the major portion of the slider pad. As suggested by the pressure profiles accompanying FIGS. 3A and 3B the outlet grooves are most advantageously placed at 0.5 to 0.8 of the total slider pad width as measured in the direction of fluid flow.

The attractive features of the pump of this invention are its simple construction and great flexibility of operating parameters. For instance, the spacing between the rotor plate and the slider pad plate can be continuously varied by external adjustment Without interrupting the operation of the pump. A wide variety of pressure-fiow rate combinations is available through variable rpm. and plate spacing. Since there are no size limitations to this principle of pump operation, pressure and output flow rate can be theoretically increased to any value.

The following is illustrative of a specific pumping operation utilizing a device constructed according to this invention.

Lubricating oil having a viscosity of l poise at room temperature was pumped in the device of FIG. 1 in which the slider pad plate and the rotor plate diameters were 3.00 in. The slider pad plate was constructed with 8 pads, each having an average width of 1.0 in. The pad construction was that of FIG. 3A wherein the slope of the pad was 0.002 in. The gap distance between the heel of the pad and the rotor plate was also 0.002 in. The outlet slot was positioned approximately in the middle of the pad. It was generally found that the position of the outlet slot is most advantageously located at a position from 0.5 to 0.75 of the distance from the feed slot.

With a rotor plate velocity of 2000 rpm. the oil velocity is 12,600 in./min. The maximum flow rate at zero pressure is 100 in. /min. The maximum pressure at zero flow rate is 100 p.s.i. These are limiting conditions which prescribe a linear function of flow rate vs. pressure. For example, at 50 p.s.i. the flow rate is 50 in. /min.

A preferred form of the device of this invention is shown in FIG. 4. This device is specifically adapted for the extrusion of plastics. Its operation is basically the same as the pump described above; however, certain structural details have been added or modified to provide for this specific application.

FIG. 4 shows a housing 70 having an interior cylindrical chamber 71. Rotatably mounted in the housing with the aid of bearing 72 is a rotor shaft 73 threaded into the rotor plate 74. The slider pad plate 75 is mounted on a header plate 76 at the head of the chamber 71 facing the rotor plate surface. To permit the use of various slider pad plate designs in this assembly, it is convenient to construct the slider pad plate separate and removable from the header assembly. However, these parts may be made integral where no such design variation is contemplated. This particular extruder utilizes a slider pad plate having slider pads of the type shown in FIG. 3B. This is a parallel stepped construction and was found particularly well suited for plastics extrusion. The slider pad plate design is shown in greater detail in FIG. 5. Returning to FIG. 4, a peripheral feed rather than a central feed is used since feed material for extruders is usually in solid form as pellets or granules and the peripheral feed arrangement shown in FIG. 4 permits a convenient gravity feed arrangement. The material flow pattern is made somewhat simpler with peripheral rather than axial feed since the central or axial region of the header assembly is most advantageously used to express the material through radial channel 79 and die 80. The head plate 76 is beveled around its periphery as shown to accommodate the feed material introduced from hopper '77 through inlet port 78 onto the slider pad plate. Inset within the header plate 76 is an insulating ring 81. This insulator aids in maintaining two temperature zones, a cool zone at the extreme periphery of the feed path and a hot zone from the pressure build-up region through the remainder of the flow path. Contributing to this temperature differential is the heat generated due to the shearing of the plastic material itself. Heater elements 82 and 83 assist in maintaining the material plastic. Current to the heater 83 is supplied by commutator rings not shown. Cooling jackets 84 and 85 maintain the periphery of the feed area cool so that the plastic is not significantly heated prior to contacting the rotor plate. The cooling jacket serves the additional function of a retaining ring and is shown bearing against the rotor plate to prevent the flow of material to the space behind the rotor plate. The cooling-jacket retainer ring is spring loaded by compression springs 86 and 87 and adjustment screws 88 and 89 so that contact with the rotor is maintained when the rotor is adjusted axially. A clean-out port is provided at 90.

The slider pad plate for the extruder of FIG. 4 is shown in greater detail in FIG. 5. This plate consists of eight stepped sections. Considering a single section 91, the feed material is drawn into the feed groove 92 and radially across the pads by what is known as the normal force effect. This phenomenon dictates that the force which is exerted upon the plates acts in a direction perpendicular to the shearing stress. Thus when a viscoelastic medium is sheared by the rotational forces of the plates it is continuously drawn toward the axis of rotation. The elastic properties of the plastic draw it onto the first stepped portion 93 of the slider pad plate. The pressure is generated by the rotation of the rotor plate forcing the material onto the raised portion 94 according to the principle illustrated by FIG. 3B which portion is constricted with respect to the rotor plate and the plastic is continuously discharged through the exit slot 95 and into the associated radial channel 79. For extruding viscous materials such as plastics the feed grooves 92 are preferably at least mils in depth.

Although this particular design which utilizes a parallel stepped slider pad has been found successful, other slider pad designs are also useful. Again it is only necessary that the gap between the rotor plate and the slider pad plate have a varying space with the output port located intermediate a region of greatest spacing and a region of least spacing. Specific minimum spacings found useful for extruding plastic materials are of the order of 0.015 in. to 0.025 in.

As illustrative of a particular extrusion operation the following example is given.

The pump design used here had a slider pad plate and rotor plate diameter of 6 in. The slider pad plate carried 8 pads with an average pad width of 2.5 in. The height of the step (65 in FIG. 3B) was 0.020 in. and the gap spacing (at 66 in FIG. 3B) was 0.060 in. The outlet slot was formed adjacent the step and was spaced at a distance of approximately 1.4 in. from the feed slot. This type of construction was found useful for extruding a variety of polymers such as low-density polyethylene, high-density polyethylene, expanded polyethylene, polystyrene, solid or expanded polypropylene, cellulose acetate, cellulose acetate butyrate, and nylon. The operating characteristics for polyethylene, for instance, are the following:

Viscosity: 10 poise Rotor plate velocity: 200 r.p.m.

Output velocity: 42 in./sec.

Maximum flow rate at zero pressure: 8.4 in. /sec. Maximum pressure at zero flow rate: 1700 p.s.i.

critical but becomes the dominant factor at high pressures.

Various other modifications and extensions of this in vention will become apparent to those skilled in the art. All such variations and deviations which basically rely on the teachings through which this invention has advanced the art are properly considered within the spirit and scope of this invention.

What is claimed is:

1. A hydrodynamic device comprising a fluid-tight housing, a first disk member and a second disk member spaced from said first disk member in said housing, both disks being coaxially disposed, at least one of said disk members having a non-planar surface such that the spacing between said disk members converges in the same cir cumferential direction, means for introducing feed material into the space between said disk members approximately at the point of greatest separation between the disks, outlet means for discharging the fluid from a position of lesser separation between the disks and means for imparting relative rotary motion between said disk members, relative rotation between said disk members causing the generation of pressure in the converging space between said disk members.

2. The device of claim 1 wherein the spacing between said disks is adjustable by axially displacing one disk with respect to the other.

3. The device of claim 1 wherein the outlet means communicate with a central bore extending through the non-planar disk to the exterior, said bore terminating in a die for expressing the desired shape.

4. The extruder of claim 3 wherein the spacing between said disks is adjustable by axially displacing one disk with respect to the other.

5. The extruder of claim 3 further including heating means located adjacent to the central axial portions of said disks and cooling means located around the periphery of said disks.

6. The extruder of claim 4 including a retainer ring disposed between one of said disks and the internal surface of said internal chamber so as to prevent the flow of feed material into the space between said disk and the housing, said retainer ring being biased against said disk by spring loading means so as to allow for the axial displacement of said disk.

7. A hydrodynamic pump comprising a fluid-tight housing having an internal cylindrical bore, a slider pad plate afiixed to one head of said cylindrical bore, a cylindrical rotor plate rotatably mounted coaxially within said cylindrical bore and spaced from the slider pad plate, a plurality of sections juxtaposed circumferential-1y over the surface of the slider pad plate, each of said sections ris ing circumferentially from edge to edge, in the same direction, such that the spacing between each of said sections and said cylindrical rotor plate converges in a circumferential direction, means for imparting rotary motion to said rotor plate, the rotary motion causing the generation of pressure in the converging space between each of the sections and the rotor plate, material feed means comprising radially extending feed grooves formed between each of said sections and terminating in a central feed chamber located adjacent the axis of the slider pad plate, an inlet port extending from the exterior through the pump housing and communicating with the central feed chamber, outlet means for expelling the fluid under pressure comprising radially extending slots formed in said sections, a channel associated with each of said slots and communicating with a common circular output channel, and output port extending from said common output channel through the pump housing to the exterior.

8. A hydrodynamic extruder comprising a fluid-tight housing having an internal cylindrical bore, a slider pad plate afiixed to one head of said cylindrical bore, a cylindrical rotor plate rotatably mounted axially within said cylindrical bore and spaced from the slider pad plate, a plurality of sections juxtaposed circumferentially over the surface of the slider pad plate, each of said sections rising circumferentially from edge to edge, in the same direction, such that the spacing between each of said sections and said cylindrical rotor plate converges in a circumferential direction, means for imparting rotary motion to said rotor plate, the rotary motion causing the generation of pressure in the converging space between each of the sections and the rotor plate, material feeding means including a feed channel formed through the extruder housing and terminating adjacent the space between said slider pad plate and said rotor plate for intro ducing feed material on to the periphery of said slider pad plate, radially extending feed grooves formed between each of said sections, outlet means for expelling the fluid under pressure comprising radially extending slots formed in said sections, each of said slots cornmunicating through a channel to a central exit bore, said exit bore extending to the exterior and terminating in a die for expressing the desired shape.

9. An extruder of claim 8 wherein said sections each rise circumferentially on an incline from edge to edge each forming a wedge.

10. An extruder of claim 8 wherein said sections each rise circumferentially in a single step from edge to edge such that each section has a first planar portion and a raised second planar portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,918,208 Becker Dec. 22, 1959 3,036,434 Mark May 29, 1962 3,037,457 Sternlicht June 5, 1962 3,046,603 Maxwell July 31, 1962 3,082,476 Bunch Mar. 26, 1963 

1. A HYDRODYNAMIC DEVICE COMPRISING A FLUID-TIGH HOUSING, A FIRST DISK MEMBER AND A SECOND DISK MEMBER SPACED FROM SAID FIRST DISK MEMBER IN SAID HOUSING, BOTH DISKS BEING COAXIALLY DISPOSED, AT LEAST ONE OF SAID DISK MEMBERS HAVING A NON-PLANAR SURFACE SUCH THAT THE SPACING BETWEEN SAID DISK MEMBERS CONVERGES IN THE SAME CIRCUMFERENTIAL DIRECTION, MEANS FOR INTRODUCING FEED MATERIAL INTO THE SPACE BETWEEN SAID DISK MEMBERS APPROXIMATELY AT THE POINT OF GREATEST SEPARATION BETWEEN THE DISKS, OUTLET MEANS FOR DISCHARGING THE FLUID FROM A POSITION OF LESSER SEPARATION BETWEEN THE DISKS AND MEANS FOR IMPARTING RELATIVE ROTARY MOTION BETWEEN SAID DISM MEMBERS, RELATIVE ROTATION BETWEEN SAID DISK MEMBERS CAUSING THE GENERATION OF PRESSURE IN THE CONVERGING SPACE BETWEEN SAID DISK MEMBERS. 